(a) Field of the Invention
The present disclosure is directed to a display panel for a liquid crystal display and a manufacturing method thereof.
(b) Description of the Related Art
Liquid crystal displays are one of the most widely used flat panel displays. A liquid crystal display includes a liquid crystal layer interposed between two panels each provided with field-generating electrodes. The liquid crystal display displays images by applying voltages to the field-generating electrodes to generate an electric field in the liquid crystal layer that determines orientations of liquid crystal molecules in the liquid crystal layer to adjust polarization of incident light. The light having an adjusted polarization is either intercepted or allowed to pass by a polarizing film, thereby displaying images.
Liquid crystal displays are categorized as non-emissive displays, and in that respect, they do not produce any form of light. Accordingly, a liquid crystal display utilizes artificial light emitted from lamps of a backlight unit separately provided, or ambient light, as a light source. Depending on the light sources employed by the liquid crystal display, a liquid crystal display is classified as a transmissive liquid crystal display or a reflective liquid crystal display. The light source of the transmissive liquid crystal display is backlight, and the light source of the reflective liquid crystal display is an external light. The reflective liquid crystal display is usually applied to a small or mid-size display device. A transflective liquid crystal display has been under development. The transflective liquid crystal display uses both a backlight and an external light as the light source depending on circumstances, and is usually applied to small or mid-size display devices.
A liquid crystal display includes two display panels. One of the display panels includes gate lines, data lines, pixel electrodes, and switching elements such as thin film transistors, and the other display panel includes color filters and a common electrode. These display panels are manufactured separately, and then the manufactured display panels are assembled into a liquid crystal display. The two panels may be misaligned during assembly such that the color filters may not correspond to each pixel area, thereby causing reduction of an aperture ratio.
In addition, the first mentioned display panel includes a plurality of pixels having switching elements and a plurality of display signal lines, and a gate driver having a plurality of stages transmitting gate signals to gate lines of the display signal lines to turn on/off the switching elements of the pixels.
Each stage of the gate driver is connected to one of the signal lines, and the stage receives a gate on/off voltage and a clock signal and transmits the inputted gate on/off voltage and clock signal to the signal line connected thereto. If the gate driver is formed outside of the substrate, pad portions, which connect the gate on/off signal lines to the stages of the gate driver, are required for transmitting the gate on/off voltage to the stages of the gate driver. Here, for connecting the pad portions to the signal lines, contact holes exposing the signal lines are formed, and then the signal lines are connected to the stages of the gate driver through the contact hole using a connecting member made of indium tin oxide (ITO), etc.
As the lengths of the signal lines increase along with the liquid crystal display size, which increases resistance of the lines, a signal delay or a voltage drop occurs due to the increased resistance. Wiring made of a material having low resistivity, such as aluminum (Al), is used.
However, if the signal lines including Al are directly contacted to ITO used in pixel electrodes or connecting members of a liquid crystal display, then the Al may become oxidized or corroded. Also, alignment errors may occur during assembling the two display panels, thereby causing a reduction of aperture ratio.